Shakespearean poem (6)
I believe the answer is:
sonnet
'shakespearean poem' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sonnet that I've seen before include "14-line poem" , "Poem of 14 lines - Shakespeare wrote lots" , "Short poem with 14 lines" , "Poem of fourteen lines" , "Fourteen line poem" .)